US4466498A - Detachable shoe plates for large diameter drill bits - Google Patents

Abstract

Shoe members and drill shank members for large diameter cable drilling bits are provided with a tongue on one of the members that projects axially relative to the drill shank member and with an arcuate lip and projecting stop on the other of the members to trap the tongue and prevent radial movement of the shoe member in response to radially directed forces caused by the spinning of the bit in drilling operations. Such forces would impose shear stresses on the fastening members that extend through the shoe member and axially into the drill shank. Four embodiments are disclosed: a spudding bit, two star bits and a scow bit.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to drill bits for gravity-drop cable drilling.

2. Description of the Prior Art

The technique of cable drilling uses a large relatively heavy drill bit that is suspended from a cable drill rig and dropped a distance of twenty-four to thirty-six inches into the bottom of the hole being drilled. The drill bit is dropped at a rate of thirty to sixty times per minute and a spin is imparted to the drill bit as it is dropped to cut a hole of circular cross section with a drill bit of less than circular cross section. Drill bits can be made in an integral construction with hardened cutting edges or blades, but these become dull and worn, and the driller is faced with the repair or replacement of a rather bulky item. Therefore, it has become a practice to mount detachable cutting members on the body of the drill bit.

Cable drilling gets its name from the cable on which the drill bit is suspended from the boom of a cable drilling rig. This type of equipment is more economical for drilling a well hole of relatively large diameter and substantial depth than rotary percussion equipment that is typically used in mining and construction. Such rotary percussion equipment is mounted on over-the-road vehicles, off-the-road vehicles or platforms and uses a string of drill pipes which must reach from the drill rig to the bottom of the hole and which must be driven by motors for both vertical and rotating movement. To drill holes of large diameter would require drill pipes that would be quite large and heavy, whereas in cable tool drilling the drill pipes are replaced by a wire line.

As seen in Sanderson, U.S. Pat. No. 1,995,043 and Sanderson, U.S. Pat. No. 2,022,055 early detachable blades for percussion drill bits were formed as wedge-shapd members with a cutting edge. Two such bits were later employed in cable drilling in a staggered configuration as shown in one of my prior U.S. Pat. No. 3,545,554. A further development in rotary percussion drilling was the provision of pivotable steel plates with tungsten carbide inserts as seen in Stebley, U.S. Pat. No. 3,536,150. These inserts are much harder and more durable than the steel plates in which they are embedded and provide greater efficiency in cutting through hard earth formations. In Stebley, the rotary percussion drill bit is reciprocated a distance of only three to five inches at a rate of 500-800 impacts per minute. The bit is rotated at 20 revolutions per minute or no more than 9 degrees per impact.

Cable drills, on the other hand, are provided with a means for winding up the cable during the lifting stroke and for imparting a spinning action to the drill bit as it travels through the downstroke to the bottom of the hole. This provides shear stresses of a magnitude unique to cable drilling against elongated axial fasteners that are used to attach metal plates to the bottom of the drill bit. The primary cutting members in Stebley are made pivotable and do not employ axial fastening members. Fixed drill plates with tungsten carbide inserts have not been known in larger sizes for cable drilling because a workable configuration for use of such plates with the bits commonly used in cable drilling operations has not been known. These commonly used bits include two-winged spudding bits, four-winged star bits and hollow scow bits.

The scow bit is a specialized bit with a hollow barrel section in which water and cuttings that have been mixed into a slurry in the bottom of a hole can be evacuated. This is accomplished by the bailing action of a valve within the barrel section that is forced open on the downstroke and pulled closed on the upstroke to trap a portion of the slurry. Kita et al., U.S. Pat. No. 4,083,415 shows a mining bit with a central opening like a scow bit, however, the Kita drill bit is rotated in small increments while in contact with the work, which is a different type of drilling action than found in cable drilling. Also in Kita, the detachable portion of the bit is formed in the shape of a cup which fits over one end of the drill bit shank and is held in place by balls that are received in a groove around the outside of that shank. Kita does not address the problem of forces on axial fasteners for plates used in the cable drilling environment.

SUMMARY OF THE INVENTION

The invention resides in a drill bit for gravity-drop cable drilling in which one or more detachable shoe members with hardenable inserts are removably attached by axially extending fasteners to a bottom diametrical portion of a shank member to form the drill bit. One of these members has a radially extending tongue that projects axially relative to the shank member and is received in a depression in between an arcuate lip and a stop formed on the other member. In one embodiment this stop takes the form of a second arcuate lip. This combination restrains the shoe plate member from movement in the radial direction where the greatest shear forces are experienced.

The invention further resides in various embodiments of the shoe members adapted for use in such drill bits as a spudding drill shoe member, a star drill shoe member and a scow drill shoe member.

A further aspect of the invention in the shoe member is the provision of means restraining the member from rotational movement due to torsional forces.

A further aspect of the invention is the provision of cutter blades for large diameter drill bits that can be attached to the bottom of the drill bit shank and located between the shoe members to cut the center of the hole being drilled. These can be mounted to the inside of the shoe plate or formed integrally in a scow shoe and positioned to cover a diametrical support.

One general object of the invention is to provide an economical, replaceable carbide-studded shoe member for cable drilling of large diameter holes. Large diameter in this instance refers to holes twelve inches in diameter or larger.

Another general object of the invention is to provide a cable drilling tool for faster drilling of wells and elevator shafts. The drill plates of the present invention have been shown to be especially effective in drilling through lava rock formations.

Another object of the invention is to permit the retrofitting of large diameter steel bit bodies with highly efficient carbide-tipped drill bits.

Another object of the invention is to provide shoe members which are easily removable and attached by use of conventional fasteners such as socket-head cap screws.

Still another object of the invention is to provide a drill bit for drilling large diameter holes with drilling machines of limited weight capacity in which spudding bits and star bits of non-circular cross section can be used to drill holes of circular cross section and maximum diameter.

The foregoing and other objects and advantages of the invention will appear in the following description, wherein reference is made to the accompanying drawings that form a part hereof, and in which there is shown by way of illustration three preferred embodiments of the invention. These embodiments, however, do not necessarily represent the full scope of the invention, but are merely illustrative, and therefore reference is made to the claims at the end of the description for determining the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a first embodiment of a drill bit of the present invention that is suspended from a cable drilling rig;

FIG. 2 is a bottom view of the drill bit of FIG. 1;

FIG. 3 is a bottom view of a shank of the drill bit of FIG. 2 with the shoe plates removed;

FIG. 4 is a fragmentary sectional view taken in the plane indicated byline 4--4 in FIG. 2;

FIG. 5 is a detail view of an area where the shoe plates are mounted on the shank of the drill bit seen in FIG. 1;

FIG. 6 is an exploded bottom view of a second embodiment of a drill bit incorporating the present invention;

FIG. 7 is an end view of one of the elongated cutter plates that was exploded from the bottom of the drill bit in FIG. 6;

FIG. 8 is a fragmentary sectional view taken in the plane indicated byline 8--8 in FIG. 6;

FIG. 9 is a perspective view of one of the shoe plates seen in FIG. 6;

FIG. 10 is an elevation view of a third, scow drill embodiment that incorporates the present invention;

FIG. 11 is a perspective view from the bottom end of the drill bit of FIG. 10;

FIG. 12 is a perspective view of the mating portions of the shank and shoe plates of FIGS. 10 and 11;

FIG. 13 is a perspective view of a fourth embodiment of the invention in which a single shoe plate is detachably mounted in a start drill bit; and

FIG. 14 is a sectional view taken in the plane indicated byline 14--14 in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first embodiment of the invention is seen in FIG. 1, where aspudding drill bit 10 is suspended by a woven, steel cable 11 from the boom of a cable drilling rig (not shown). The spuddingbit 10 includesdetachable shoe plates 13 which are fastened to the bottom of adrill bit shank 14 with socket-head cap screws 15 seen in FIGS. 2 and 4. As seen best in FIG. 4, thesescrews 15 are inserted upward through theplates 13 into tapped holes in thedrill shank 14 which are parallel to its longitudinal axis. The heads of thescrews 15 are received to some depth within the counterbores ofholes 36 in theplates 13. In this instance there are fivesuch holes 36 in each plate as seen in FIGS. 2 and 3.

Thedrill bit 10 is coupled to the cable 11 by awire rope socket 16. FIG. 1 shows thelower end 17 of a drill body with an internal hammer as shown and described in my prior U.S. Pat. No. 4,440,245, issued Apr. 3, 1984. The drill body is connected between therope socket 16 and a threaded tip (not seen in FIG. 1) of thedrill shank 14 and adds a chattering effect to each blow or drop of thedrill bit 10.

Thedrill bit 10 is used to drill well holes and elevator shafts by dropping it a distance which is typically twenty-four to thirty-six inches, at a rate which is typically thirty to sixty times per minute. As the steel cable 11 is lifted on the upward stroke of the drill cycle, the rig causes the cable to be wound or twisted in the clockwise direction (as viewed in FIGS. 2 and 3). When thedrill bit 10 is dropped it spins counterclockwise. This spinning action causes the right-hand threaded connection to the drill body and the right-hand threadedscrews 15 to tighten and allows the spuddingbit 10, which is of non-circular cross section, to cut a hole of circular cross section.

Theshank 14 of thespudding 10 is elongated with acylindrical stem 21 and abody 22 of larger diameter than thestem 21, but of non-circular cross section. Thebody 22 has two large axially extending andoppositely facing concavities 23 which are positioned at right angles to a pair ofcutter wings 24 extending in opposite radial directions. Theconcavities 23 provide adrill shank 14 of less mass for a given diameter and of non-cylindrical shape which overcomes the problem of suction that would otherwise occur when thebit 10 was in a hole. Some liftingfins 25 are welded to the sides of thedrill shank 14 within theseconcavities 23 to dislodge and carry upward loose pieces of the earth formation being drilled.

Referring now to FIG. 2, theshoe plates 13 are fan-shaped members that extend radially outward from a straight, inwardly facing side along itsheel 26 to an arcuate, outwardly facing side along itstoe 27. Theheel 26 andtoe 27 are formed with oblique surfaces on their bottom peripheral edges. The body of eachshoe plate 13 is preferably made of steel. Spherical-headed stud inserts 30 of material that is harder than steel to provide longer wear, such as alloys of tungsten carbide, are press and/or shrink fitted into bores in the body of eachshoe plate 13. Theinserts 30 are distributed in patterns along the flat bottom surfaces of theshoe plates 13 and are also angularly positioned thirty-five degrees from vertical to project from the oblique surfaces along theheel 26 andtoe 27 of the body of eachshoe plate 13. Each of theplates 13 also contains a pair of downwardly facingconcave portions 31 along opposite radial sides in which no inserts are positioned. The outwardly facing peripheral surface of thetoe 27 has flat-headedinserts 28 andvertical grooves 29 to reduce wear on this surface. Theheel 26 of eachshoe plate 13 abuts a rectangular, dependingstop 33 that extends along theheels 26 of theshoe plates 13.

As seen in FIG. 3 with theshoe plates 13 removed, a conventional spudding bit has been converted to ashank 14 for the present bit by forming arcuate dependinglips 34 on the outer peripheral edges of thecutter wings 24. A pair of fan-shaped recesses are defined by thelips 34, thecentral stop 33 and two fan-shaped surfaces which shall be referred to aspalates 35. Fan-shapedtongues 32 are formed by raised portions of theshoe plates 13 as seen in FIG. 4 and thesetongues 32 are received against thepalates 35 on the bottom of thedrill shank 14 to secure theshoe plates 13 against movement either inwardly or outwardly in the radial direction. Although the invention is particularly aimed at preventing the movement of theplates 13 in a radial direction, one further aspect concerns securing theplates 13 against torsional forces that would be directed normal to the radial forces. As seen in FIG. 5 finger-like projections 38 extend forward from thetongue 32 on eachshoe plate 13 to catch the adjacent lower side portions of theshank 14 and prevent rotation of theplates 13 relative to theshank 14.

A second embodiment of the invention is seen in FIGS. 6-9 in which four identical shoe plates 39 (one of which is shown in full) are fastened to the bottom of the star drill bit that forms adrill shank 40 for the present invention. Theshank 40 is similar to that seen in FIG. 1 in having a stem, however, the body of theshank 40 is formed with fourcutter wings 42 instead of two. Thesecutter wings 42 are each formed symmetrically along one of two orthogonal, transverse axes so that thecutter wings 42 are angularly spaced at ninety degree intervals. Eachcutter wing 42 has a radially extending web 43 and a widerarcuate section 44 at its radial extremity. Each of the fourshoe plates 39 covers a portion of the bottom of the web 43 as well as covering thearcuate section 44 at its radial extremity. This leaves a cross-shaped portion of the shank bottom to be covered by an elongatedcentral cutter plate 45 and two shorterwing cutter plates 46. With thelarger shoe plates 39 spaced apart by about seven inches in a twenty-two inch to thirty inch diameter drill bit, thesmaller cutter blades 45 and 46 provide for the effective drilling of the center portion of the hole.

As seen in FIG. 9, the body of eachshoe plate 39 has anarcuate lip 47 along the upper front edge of itstoe 48 and astraight abutment 49 along the upper front edge of itsheel 50. Thetoe 48 has flat-headedinserts 51 of hardened metal projecting a short distance from its outer peripheral face. Anoblique surface 52 is provided around the lower front edge of thetoe 48 so that spherical headedinserts 30 of carbide metal can project at an angle thirty-five degrees from vertical as described for the first embodiment. The front of theheel abutment 49, the back of thelip 47 and apalate surface 54 define a recess in the top of theshoe plate 39 which receives atongue 55 of corresponding shape that depends from the bottom of thecorresponding cutter wing 42. Theshoe plates 39 are fitted over thesetongues 55 and are secured to the bottom of the shank by socket-head cap screws 15 seen in FIGS. 6 and 8 which extend upwardly into counterbored and tappedholes 56 parallel to the axis of thedrill shank 40. When theshoe plates 39 are mounted on the bottom of theshank 40, they are restrained against outwardly directed radial movement by theheel abutment 49 and are further restrained against inwardly directed radial movement by thelip 47. From the first two examples of the invention it will be seen that the tongue can be formed on either a drill shank or a shoe plate and the lip and cooperating stop can be formed on the other of these members.

Thesmaller cutter blades 45 and 46 are formed in a generally rectangular box shape except for oblique surfaces 57 extending along the sides of thebottom surface 58. Spherical-headed stud inserts 30 of carbide metal project from thesesurfaces 57 at an angle of 35 degrees from vertical. Some of these stud inserts 30 also depend vertically downward from theflat bottom surface 58. The bottom of theshank 40 has elongated milledgrooves 59 disposed in the pattern of a cross to receivemating projections 60 on thecutter blades 45 and 46. Thecentral cutter blade 45 extends across the center of theshank 40 from onelarge shoe plate 39 to anopposite shoe plate 39, and twowing cutter blades 46 fill thespaces 39 between thecenter cutter blade 45 and the twoshoe plates 39 spaced on opposite sides of thecenter cutter plate 45. Thecutter blades 45 and 46 are attached withbolts 15 which extend through counterboredholes 61 similar to the attachment of theshoe plates 39.

A third embodiment of the invention is ascow drill bit 62 that is seen in FIGS. 10-12. The scow bit is a specialized bit in which thebody 63 of thedrill shank 64 is formed as a hollow barrel in which water and cuttings that have been mixed into a slurry in the bottom of a hole can be evacuated. If enough of this slurry accumulates it may exit the drill stem through thegrate 80 in FIG. 10. The upper portion of theshank 64 is formed with acylindrical stem 65 and a threadedupper tip 66 that can be received in a drill body as described for the embodiment in FIG. 1. Thescow bit 62 has a plate valve (not shown) within thebody 63 that is forced open on the downstroke of thedrill bit 62 and pulled closed on the upstroke to trap a portion of the slurry.

As seen in FIG. 11, asingle shoe plate 68 with two kidney-shapedopenings 69 is preferred for thescow bit 62. The body of theshoe plate 68 has an annular outer portion 68a and a diametrical center portion 68b that is formed integrally with the annular outer portion 68a. Spherical-headedinserts 30 of carbide metal are mounted to project downward from the bottom of both portions and anoblique surface 68c is formed around the circumference of the annular portion 68a to carryinserts 30 that project at an angle from vertical to cut the sides of the hole. Flat-headedinserts 81 are mounted to project radially from the outer periphral surface of thecylindrical shoe plate 68. It is preferred, but not required, thatseveral indentations 70 be provided around the outer peripheral surface of theshoe plate 68 to overcome the effects of suction in the bottom of the hole. These indentations may be aligned withchannels 71 in a reinforcedportion 72 of slightly greater diameter than the main portion of thebody 63 as seen in FIG. 10. This reinforcedportion 72 carries four dependingarcuate lips 73 on its lower end which are separated by thechannels 71 as seen best in FIG. 12.

The lower end of thedrill shank body 63 also has a bottom diametrical portion which includes asupport bar 74 across the entrance into its hollow body portion. Thissupport bar 74 extends downwardly, as do thearcuate lips 73, beyond an annular recessedsurface 75 around the bottom of thedrill shank body 63. Theannular shoe plate 68 has a ring-shapedprojection 76 that is received in theannular recess 75. Theshoe plate 68 has counterboredholes 77 through its ring-shapedprojection 76 which are spaced around it at regular angular intervals. A corresponding set of tapped holes 78 is provided in the recessedsurface 75 so that socket-head cap screws 15 can be used to fasten theshoe plate 68 to the body as seen in FIG. 11. When theshoe plate 68 is mounted on thedrill shank 63 thesupport bar 74 provides backup support for the diametrical center portion of the shoe plate 78. Analogous to the other embodiments, theshoe plate 68 will be restrained against inward radial movement by the projectingdiametrical support 74 and against outward radial movement by abutment with thearcuate lips 73. This reduces the shear forces that would otherwise be exerted on the cap screws 15.

A fourth embodiment of the invention is seen in FIGS. 13 and 14, where astar drill shank 82 has a single, four-winged, carbide-studded shoe plate 83 detachably mounted by socket-head screws 15. Such an arrangement is used for drilling smaller holes than the structure seen in FIGS. 6-9. Because asingle plate 83 is used, separate cutter blades and additional abutments are not seen at the bottom center of thedrill shank 82.

As illustrated by FIG. 14, a star-shapedtongue 84 is formed on the bottom end of thedrill shank 82 and four projectingarcuate lips 85 are formed on the upper front edges of the toes of the fourrespective blade portions 83a of theshoe plate 83. Since thearcuate lips 85 are disposed to abut oppositely facing sides of thetongue 84 they restrict theplate 83 from movement in either direction along a diameter of theshoe plate 83. It can be seen from this embodiment how a secondarcuate lip 85 opposite afirst lip 85 performs the function of the central abutment in other embodiments. The central abutments are nevertheless important additions to bits with multiple shoe plates.

With this description of several illustrations of the invention, it should be apparent to those skilled in the art that other embodiments are possible without departing from the principles of the invention. Therefore, the following claims are provided to define the scope of what I regard as my invention.

Claims (10)

I claim:

1. An improved drill bit for gravity-drop cable drilling, the bit comprising:

an elongated shank member having a bottom diametrical portion;

a shoe member with a metal shoe body and with inserts of a metal that is harder than the metal of the shoe body, some of the inserts projecting at an angle from a bottom of a toe on the shoe body, these angularly projecting inserts being operable to cut along an outer edge of a hole being drilled;

fastener means extending through the shoe member and into the shank member in an axial direction relative to the shank member for removably coupling the shoe member in a fixed position along the bottom diametrical portion of the shank member;

wherein one of the members coupled together by the fastener means has a tongue projecting axially relative to the shank member and disposed longitudinally relative to the bottom diametrical portion of the shank member; and

wherein the other of the members coupled together by the fastener means has an arcuate lip that opposes a radially outward facing side of the tongue and also has a projecting stop that opposes a radially inward facing side of the tongue to cooperate with the lip in restraining radial movement of the shoe member along the bottom diametrical portion of the shank member in response to radial shear forces encountered during cable drilling operations.

2. The improved drill bit of claim 1, wherein the lip and projecting stop are formed on the bottom diametrical portion of the shank member and wherein the tongue is formed on the shoe member.

3. The improved drill bit of claim 2, wherein: the shank member has openings on opposite sides of the bottom diametrical portion into a hollow portion;

wherein the lip is divided into four angularly spaced apart arcuate sections;

wherein the tongue is annular in shape and is received against the bottom diametrical portion of the shank member between opposing arcuate sections;

wherein the bottom diametrical portion provides a projecting support; and

wherein the shoe member has a cutter blade portion extending across the projecting support.

4. The improved drill bit of claim 2, wherein:

the bottom diametrical portion of the shank member has two cutter wings extending in opposite radial directions;

further comprising a second shoe member; and

wherein the first-mentioned shoe member and the second shoe member each have an axially projecting tongue that is received and positioned between a projecting stop and a lip on a corresponding cutter wing.

5. The improved drill bit of claim 1, wherein the lip and projecting stop are formed on the shoe member and wherein the tongue is formed on the bottom diametrical portion of the shank member.

6. The improved drill bit of claim 5, wherein:

the shank member has a second bottom diametrical portion crossing the first-mentioned bottom diametrical portion, the bottom diametrical portions forming four radially extending cutter wings;

further comprising three shoe members in addition to the first-mentioned shoe member, each of the four shoe members having a lip and a projecting stop; and

wherein each cutter wing has a radially directed tongue that is received in position between the lip and the projecting stop of a respective shoe member.

7. The improved drill bit of claim 1, wherein:

the shank member has a second bottom diametrical portion crossing the first-mentioned bottom diametrical portion to form four radially extending cutter wings;

further comprising three shoe members in addition to the first-mentioned shoe member;

wherein each shoe member is mounted at a radial extremity of a respective one of the four cutter wings to provide a cross-shaped gap in between the cutter wings; and

wherein cutter blade means with carbide metal inserts spans the cross-shaped gap to cut the center portion of the hole being drilled.

8. The improved drill bit of claim 1, further comprising a second shoe member;

wherein the shoe members have respective heels which are spaced apart to provide a gap, the shoe members extending from their respective heels in opposite radial directions along the bottom diametrical portion of the shank member; and

wherein a central cutter blade with projecting hardened metal inserts is mounted to the bottom of the shank member in the gap to cut the center portion of the hole being drilled.

9. The improved drill bit of claim 1, further comprising means formed along the radially extending sides of the shoe member and along adjacent sides of the shank member to restrain the shoe member against rotation in response to torsional forces.

10. The improved drill bit of claim 1, wherein the first-mentioned lip is disposed at one end of the bottom diametrical portion of the shank member; and

wherein the projecting stop is a second arcuate lip disposed at an opposite end of the bottom diametrical portion of the shank member.

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